Extraction of hydrocarbon material with light hydrocarbons



May 28, 1940. w. K. L Ewls E1 AL EXTRACTION OF HYDROCARBON MATERIAL WITH LIGHT HYDROCARBONS Filed Sept. '7, 1934 ZONE PR o PA ME SUPPL r TA Nk Patented May 28, 1940 PATENT OFFICE MAL wrm LIGHT mmnoc Warren K. Lewis, Newt Whiteley, Roselle, N.

Oil Development Company,

Delaware F HYDROCARBON MATE- ARBONS on, Mass.,` and James M. J., assignors to Standard a corporation of Application September 7, 1934, Serial No. 'Z4-3,046-

16 Claims.

- This invention relates to the treatment of hydrocarbon oils with light hydrocarbons, and is more particularly concerned with the extraction of such oils with light hydrocarbons at high temll peratures and at varying pressures.

`Light hydrocarbons exert under suitable conditions a selective solvent action on heavier hydrocarbon oils whereby the latter may be separated into-fractions having dierent characteristics. The density of the particular light hydrocarbon solvent used has an .important effect upon the degree of separation obtained. Thus, in vgeneral the lower the density of the light hydrocarbon solvent the greater will be the u proportion of theoil thrown out in the bottom or heavier layer. Similarly `the higher the density the greater will be the proportion of the oil remaining in the upper or lighter layer.

Several methods of causing a. variation in the density o1.' the light hydrocarbon solvent have been proposed. One methodis to vary the temperature at which the extraction is carried out.

Another method is to Vary the proportion of Y lighter and heavier hydrocarbon components of the light hydrocarbon solvent.

We have now found a new method for varying the density of the light hydrocarbon solvent. This method is to vary the pressure under which the solvent is used. It is particularly useful when 3 the temperature of treatment is within 50 or 150 F. below the critical temperature of the lighthydrocarbon solvent.

In a copending application of Warren K. Lewis, u Serial No. 739,226, led August 10, 1934, a.` method of treating hydrocarbon oils with light hydrocarbons has been described which comprises carrying out the treatment at the critical teinperature or above of the light hydrocarbon, and varying the pressure maintained at these temperatures. At the critical temperature or above, 1 the pure undissolved light hydrocarbon exists entirely as a single homogeneous phase. The effect ot increasing pressure in the presence of heavier hydrocarbons is to cause the light hydrocarbon vapor todissolve therein. By a sufficient increase` in pressure enough light hydrocarbon may be f caused to dissolve in the heavy oil to effect a separation thereof into two layers.

The present method is differentiated from the foregoing method in that the treatment is carried out at high temperatures below the critical temperature of the light hydrocarbon so that it is possible to retain the4 light hydrocarbon in `5g the liquid phase.

(Cl. 19e- 13) y The nature of the present -processfand the method of carrying it out will lbe fully understood* from the following description read with reference to the accompanying drawing which is a semi-diagrammaticai view in sectional elevation of a type of apparatus suitable for the purpose.

For convenience in description the light hydrocarbon solventfwill -be denoted by the word propane, but lit should be understood that this does not limit the process to the use of propane only.` Similarly the initial material to be treated will'be denoted by the word ,oilf Referring to the drawing, numerals I designate supply tanks of liquid propane, andnumeral 2 ldesignates a supply tank ofvoil to be treated. Numerals 3, 4,- 5 and 6 represent treating towers adapted to withstand `pressures as high as 100 atmospheres or mor-e and temperatures as high as 500 F. or more. 'Ihe treating, towers 3,4, 5 and 6 are provided with coils 1, 8, 9 and yI0 respectively disposed within them and adapted to be provided either with heating mediaor cooling media by means of which the. temperature within the towers may be adjusted andv controlled. Pump Il withdraws propane froml tanks I through line I2. Pump I3 withdraws oil from tank 2 through line I4. Pumps Il and I3 force Lliquid propane and oil respectively under pressure through lines I5 and I6 vrespectively into and through a mixing device Ila such as a series of orifices and thence through a heating means Il wherein' the 'mixture of oil and propane is brought to a temperature within about 50 or 100 F. below the critical temperature of propane. From the heater the mixture of oil and propane discharges through line I8 into treating tower 3. In tower 3, heavy asphaltic bodies which are precipitated by the propane and remain undissolved settle to the bottom and are removed through line I9.

The solution of oil and propane free from undissolved asphalt is withdrawn from tower 3 through line 20, If the next tower is to be maintained under a lower pressure than thatmainpressures, the mixture from tower 3 will iiow through line into tower 4 under reduced pressure. In tower l, the oil will be caused by the reduction in pressure to separate into two layers. The extract or bottom layer comprising the heavier fractions of the oil is withdrawn through line 23.

The upper layer is withdrawn from tower l through line 24 provided with pressure reduction valve 24a and by-pass line 25 provided with pump 25a. Thence it discharges under reduced pressure into tower 5 in which another separation into layers is induced by the reduction in pressure, The bottom layer is removed through line 26 and the upper layer through line 21, provided with pressure reduction valve 21a and by-pass line 28 provided with pump 23a.

Thence the upper layer from tower 5 discharges into tower 6. Another separation is induced by the reduction in pressure. Thebottom layer is withdrawn through line 29, and the top layer through line 30 provided with pressure release valve 30a. and by-pass line 3| provided with pressure pump 3io.

The upper layer from tower 6 may be forwarded to another tower and as many succeeding towers (not shown) as desired. If tower 6 is to be the last tower then the upper layer withdrawn therefrom is discharged into a separating zone 32 provided witlrhcating means 33. TheV temperature is raised in the separating zone 32 by means of heating coil 33 to the critical temperature of propane. If the-pressure in tower 6 was below the critical pressure of propane then it is increased to` that pressure by means of pump 3|a prior to discharge into separating zone 32. If the pressure-were above the critical pressure then it is reduced torthat pressure by means of pressure reduction valve 36a prior to discharge into the separating zone.

In the separating zone which is maintained at the critical conditions of propane, the oil and propane become substantially immiscible in one another, and a layer separation between the oil and propane occurs.

The oil layer which will contain a small amount o! propane, say 0.5 pound per pound of oil, may be removed from the separating zone 32 through line 34 and the last traces of propane may then be removed from the oil by distillation or other suitable means.

The propane layer is withdrawn from separating zone 32 through line 35 by pump 36 and may then be returned through line 31 to the propane supply line I5 under the required pressure.

The foregoing method of separating the propane and oil has been described in a co-pending application of .Gustav A` Beiswenger, Serial No. 626,333, led July 30, 1932, now Patent No. 2,115,003, dated April 26, 1938, and is especially convenient in the present process, but it will be understood that other methods of accomplishing the separation, such as by distillation under super-atmospheric pressure followed by condensation of the propane or by reduction of pressure to atmospheric followed by recompression of propane vapors, are not precluded.

The bottom layers removed from towers l, 5 and 6 through lines 23, 26 and-29 respectively may be subjected to the same treatment as the upper layers either under progressively decreasing orprogressively increasing pressures. -The several bottom layers may also be recycled to the next preceding towers as indicated by dotted lines 38, 29j and Il, or the several bottom layers may be mixed in any suitable proportions and all or a portion thereof may be recycled to any one or more of the towers. If desired, the oil may be recovered separately from each bottom layer.

It will be understood that the treatment may if desired be carried out in a single tower with removal of either the .top or bottom layer following each change in pressure.

Inithe operation of the process the important variables are the initial material, the light hydrocarbon used as the solvent, the temperature of treatment, the pressure maintained and the proportions of oil and light hydrocarbon.

The initial material adapted for treatment according to the present process may comprise any hydrocarbon oil such as gas oil, light lubricating oil, heavy lubricating oil, gear oil, transmission ,oil, parafiin distillate, Vresidues and the like rwhether obtained by the distillation, destructive distillation, hydrogenation, destructive hydrogenation; or cracking of coals, tars, pitches, bitumens, resins, lignites,.shales, petroleum, mineral oil and other carbonaceous materials. Also included are hydrocarbons prepared by synthetic processes such as polymerization or condensation in the presence or not of catalytic materials such as aluminum, zinc, iron, tin or boron halides; as well as hydrocarbons prepared by voltolization by means of silent electric discharges. The initial material may contain wax or asphaltic bodies or other materials since these can either be removed during the process or will not interfere materially with the operation thereof. The process is particularly adapted to the treatment of viscous lubricating fractions derived from petroleum. Y

The light hydrocarbons suitable for use vin the present process comprise hydrocarbons having between 1 and 8 carbon atoms. In general hydrocarbons having vbetween 2 and 6 carbon atoms will be preferred. As examples of suitable light hydrocarbons may be mentioned methane. ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, propylene, butylene, amylene, hexylene, heptylene, octylene, isobutane, isopentane, cyclo-hexane, isoheptane or any mixtures of two or more of these, or hydrocarbon mixtures containing a major proportion of hydrocarbons having between 1 and 8 carbon atoms- Also suitable for use as the light hydrocarbon solvent are light naphthas whether obtained naturally or by synthetic or hydrogenation processes, casinghead gasoline, natural gasoline and the like.

The gases obtained in the cracking or destructive hydrogenation of heavy hydrocarbon oils and in the stabilization or debutanization of gasolinas are generally relatively rich in the preferred light hydrocarbons and provide an especially suitable and convenient source thereof.

lThe temperature of treatment should be above the melting point of the initial material to be treated but preferably below the cracking temperature thereof. The general range of temperature will therefore be between about 50 F. and 550 F. although this is merely illustrative and not limitative. The exact temperature used will depend upon the particular light hydrocarbon or mixture of light hydrocarbons selected as the solvent. In any particular case the temperature maintained is preferably between about 150 F. or less of the critical temperature of the light hydrocarbon and just below the criticalV temperature.

Thus, Afor propane which has a critical temperature of212" F., the preferred temperature will be between about 110 F. and just below 212 F. For

density: The operating temperature in such eases will be below-'the'highest temperature Aat which vapor and liquid phases can coexist.

.The pressure maintained during the treatment is .of primary importance -in the present process because it is by means of varying the. pressure that changes in the density of vthe solution of oil in solvent which cause changes in the selectivity of the solvent are obtained. In general the pressure should be at least sufficient to retain the light hydrocarbon in liquid phase at the temperature of working. The pressure may vary from this point to pressures several times the equilibrium vapor pressure of the solvent at the temperature of working. It will beunderstoodthat the lower the molecular weight of the light hydrocabon used, the higher will be the pressure necessary to retain the light hydrocarbon in liquid phase at the same temperature of working. It will be found that a relatively` small increase in 'pressure will cause a pronounced change in the density of the light hydrocarbon. Thus with propane thepressure may be varied from say 150 lbs/sq. inch to as high as'1500 lbs. per square Y inch, although pressures between say 200 and 900 equally satisfactory results.

lbs. per square inch will give a wide variation in density at temperatures within' about 50 F. of the critical temperature'of propane.

,I The proportion of light hydrocarbon to oil may vary from 2 to 12.volumes per volume of oil although from 3 to 8 volumes per volume of oil-will be preferable in most cases. It will be understood that the volume 'of light hydrocarbon used will determine to a large extent the yield of treated oil obtained since the top layer will always be substantially saturated with lighter fractions of the oil.

One of the important features ofthe present invention is that any light hydrocarbon having between 1 and 8 carbon atoms may be used with It has beenL found that the'density of all of these light hydrocarbons is substantially the same at their respective critical temperatures and that the same solvent density may be obtained at other temperatures with any ofV these light hydrocarbons by adjusting the temperature and pressure conditions. 'I'hus if a particular solvent density is found to give the degree of separation desired this solvent density may be obtained with say heptane as well as with propane merely by ad- .justing the temperature and pressure at which the heptane is used. It will be seen that if heptane is selected as the solvent the temperature `will have to-be much higher than if propane is used to get the same solvent densityy but on the other hand the lcorresponding pressure will be much lower than is necessary with propane. Whether or not heptane is selected instead of propane will depend very largely uporrthe nature ofthe initial material and upon practicalv and economical consideration as to the availability of .heptane and the desirability of operating at higher temperatures. The important thing is that any one of these light hydrocarbons may be made to be satisfactory provided other considerations are equal. l

Similarly mixtures of two or more light hydrocarbons will operate as satisfactorilys a sintle hydrocarbon. Thus, for example a mixture of octane and ethane maybe made to approximate say propane or butanev so that the temperature and pressure condition required to obtain a particular solvent/density for the mixture may be substantially the same as those required for the single hydrocarbon. Also mixtures of -say ethane or. propaneV with hydrocarbons higher than octane may be prepared which will have ythe characteristicsv necessary for carrying out the present process. 4' The selectivity of the light hydrocarbon used in the present process may be accentuated by the `use of preferential solvents for naphthenic or aromatic hydrocarbons incombination with and together with the light hydrocarbons.l Suitable preferential naphthenic solvents for thisl purpose include Y phenols, cresols, cresylic acid, xylols, liquid sulfur dioxide, aniline, chloraniline, nitrophenols, nltrobenzene, furfural, ether, croton aldehyde, cellosolve acetate, glycol diacetate and the like as weil as what may be termed conditioned phenolic substances, that isto say substances such as phenols, cresolsy xylols and other alkylated phenols to which have been added small quantities of conditioning agents such as water, caustic soda, caustic potash,

methyl, ethyl or propyl alcohol. glycerine, ammonia `and the like. the effect oi which conditioning agents is primarily to change the miscibility temperaturesfof the oil and solvent. A

In carrying out the process the oil to be treated may be preliminariiy deasphaltized, dewaxed or otherwise treated as with acid or clay. If the oil is to be preliminar-ily deasphaltized and dewaxedr it is rconvenient to do this by means of liquidpropane or other liquefied normally gaseous hydrocarbon since the saine solvent may be Yused in the subsequent treatment according to the present process, although it will be understood that thepreliminary deasphaltizing and dewaxing may be accomplished by other means and with other solvents. Y Y a As indicatedabove, however, the deasphalting operation may be convenientl'y'included as the first operation of the present process. and in many cases` this lprocedure will be preferable to a separate preliminary deasphaltizing Ystep because the precipitation of Yasphalt at temperatures close to the critical temperatures of the light hydrocarbons is particularly effective.

Dewaxing, acid and clay treating, and general refining treatments may also follow treatment according to the present process.l The oils btained in the process may also be subjected to cracking, hydrogenation, destructive hydrogenation, polymerization, condensation or voltolization treatments. This last procedure is especiallyy useful and valuable because the products obtained from the high temperature light hydrocarbon treating are free from asphaltic and tarry impurities which are detrimental in crack-.

dichlorethyl o, propane at those temperatures when the vapors TABLE I i.

Treatment at saturation pressures Volumes Yield promille Tagli. litressur. @il sigboot agoilii'sron perro s.,sq. n. 0p t nu @780 E met? 21o F. 4(dumm) s m 315 81,4 114 2% s 162 400 75 100.5 z 185 50u 55.7 85.5 5 l2 l49 375 84 115 3 5 185 490 47.7 90.5 2

TABLE II Treatment at pressures labove saturation pressures 5 voiuma I Yield een; n tra* sais...

l' V0 5.1Sq. Xl. -OD o ml 80., F Y layer) 210 E. (diluted) 192 am 52.5 se 1an om e1 97 5% l92 850 6T 96.5 6V 180 640 58 5 105 2 4 192 850' 51.5 85.4 5%

In the above tables the term saturation pressure means the equilibriuml vapor pressure of propane at the respective temperatures. that is to say, the pressure exertedbythe vapors of are in equilibrium with liquid propane.

The present process is particularly suitable for preparing valuable hydrocarbon products.

For example, oils'of extremely high viscosity of the order of 1000, 2000, 5000 or even 10,000 seconds Saybolt viscosity at 210 F. may be obtained by subjectinga heavy hydrocarbon oil to the above described treatr'nent.V Thelighter fractions are progressively removed by the successive treatments at varying pressures, and the final bottom layer after removal of any light hydrocarbon solvent contained therein will comprise an extremely viscous oil. Such viscous oils are adapted for various special purposes and may be used as such or may be blended with lighter oils to increase the viscosity of the latter.

Another valuable use oi the present process is in the recovery of natural pour inhibiting materials from petrolatumv or materals rich in petrolatum. By repeated treatment of the petrole.- tum under progressively increasing pressures, a concentrated jform of the natural pour inhibitors contained in the petrolatum maybe obtained.

Similarly the present process is especially useful in preparing concentrated synthetic pour inhibiting agents, and in preparing concentrated products from oils prepared by voltolization and other special treating processes. Long residual oils oi low Conradson carbon content may be prepared by the present process, and the present invention contemplates the method of preparing the above products and the products themselves. This invention is not limited by any theory of -the mechanism of the process nor by any` details which have been given merely for purposes of illustration, but is limited only in and by the following claims in which it is intended to' claim allA novelty inherent in the invention.

We claim: Y

l. The method of treating hydrocarbon oils which comprises diluting the same with a light hydrocarbon solvent. heating the mixture to a high temperature below the critical temperature of the light hydrocarbon' solvent, increasing the layers.

2. The method of Vtreating hydrocarbon oils which comprises dilutingV thesame with a light hydrocarbon solvent, heating the mixture to a high temperature below the critical temperature ofthe light hydrocarbon solvent,fincreasing the pressure to-several timesthe equilibrium vapor pressure of the light hydrocarbon atthe temperlature of working, separating the two. layers formed, reducing pressure on the bottom layer whereby a further separation is caused, again separating the two layers, reducing Apressure on the bottom layer, separating the two layers, re-

ducing pressure on each layer to the critical pressureof the light hydrocarbon solvent and heating the two layers-to the critical temperature o! the solvent whereby the oilis caused to separate from the light hydrocarbon, and recovering the oil layers.

' 3; Process according to claim 1 in which the recovered light hydrocarbonv is returnedto the irst step of the process. 1

4. Process according to claim 1 in which the light hydrocarbon solvent comprises propane.

. 5. Process according-to claim 1 in which the oil is first deasphaltized by means of a light hydrocarbon. v 1

6. Process according to claim l in which a selective solvent for naphthenic hydrocarbons is used together with the light hydrocarbon solvent.

'1.'Process for separating hydrocarbon oil into two normally liquid fractions which comprises diluting the oil with a light hydrocarbon solvent, maintaining suilicient pressure to retain the light hydrocarbon solvent in liquid phase, causing a portion of the oil to be thrown out of solution by varying the pressure maintained on the mixture, separating the two liquid layers thereby formed and recovering the oil therefrom.

8. Process for separating a hydrocarbon oil in- 'to normally liquidfractions which comprises dissolving the oil in a light hydrocarbon solvent, heating the mixture to a high temperature below the critical temperature of the light hydrocarbon solvent, maintaining at least suilicient pressure to retain the light hydrocarbon solvent in the liquid Vphase at the temperature of working, eilecting a change in thedensity of the solvent suiiicient to cause a portion of the oil to be thrown outof solution solely by varying the pressure maintained thereon, separating the two layers thereby formed and recovering the oil from each layer. f

9. The method of separating a heavy hydrocarbon oil into a series of normally liquid iractions which comprises dissolving the oil in a light hydrocarbonsolvent, heating the solution to a temperature within 100 F. of the critical temperature of the light hydrocarbon solvent, maintaining a pressure at least sulicient to retain the light hydrocarbon solvent in liquidI phase at the temperature of working, progressively changing the pressure maintained, on the solution whereby vus a sufficient change in the density of the solvent is effected to cause a portion of the oil to be thrown out of solution, separating the two liquid layers formed after each pressure variation and recovering the oil from the several layers.

10. The method of treating heavy hydrocarbon oil which comprises diluting the same with several volumes of liquefied propane, heating the mixture to a temperature between and 212 F., progressively` varying the pressure between about 200 and 900 pounds per squareinch whereby the mixture is caused to separate into two layers, separating the two layers formed after each pressure variation, and recovering oil from the several layers.

11. The method of treating a heavy hydrocarbon oil which comprises diluting'the same with from 3 to 8 volumes of a. liquefied hydrocarbon solvent consisting essentially 'of butane, heating the mixture to a temperature between and -304 F., progressively varying the pressure maintained from several times the equilibrium Vvapor the wax so precipitated. heating the remaining oil solution to a temperature within about 50 F. of the critical temperature of Athe liquefied normally gaseous hydrocarbon solvent, increasing the pressure to several times the equilibrium vapor pressure of the liquefied hydrocarbon'at the temperature maintained, separating the two layers intoL which the soluton'is thereby caused to separate, progressively decreasing pressure to cause further separation into two layers, separating the two layers after each pressure variation and recovering oil from the several layers.

13. Process according to claim 8 in which the light hydrocarbon solvent comprises hydrocarbons having between l and 8 carbon atoms.

14. Process according to claim 8 in which lthe light hydrocarbon oil is diluted with between '3 andv 8 volumes or light hydrocarbon solvent per volume of oil.

15. Process according to claim 8 in which a selective solvent for naphthenic hydrocarbons is used together with the light hydrocarbon solvent.

A16. Process for treating a petroleum lubricating oil-which comprises diluting the same with several volumes of a liquefied normally gaseous hydrocarbon, subjecting the mixture to a high temperature below the critical temperatureof the wam-mix. samen. wm'rmnr. 

